Bias and sensitivity analysis when estimating treatment effects from the cox model with omitted covariates
Lin, NX; Logan, S; Henley, WE
Date: 1 December 2013
Article
Journal
Biometrics
Publisher
Wiley for International Biometric Society
Publisher DOI
Related links
Abstract
Omission of relevant covariates can lead to bias when estimating treatment or exposure effects from survival data in both randomized controlled trials and observational studies. This paper presents a general approach to assessing bias when covariates are omitted from the Cox model. The proposed method is applicable to both randomized ...
Omission of relevant covariates can lead to bias when estimating treatment or exposure effects from survival data in both randomized controlled trials and observational studies. This paper presents a general approach to assessing bias when covariates are omitted from the Cox model. The proposed method is applicable to both randomized and non-randomized studies. We distinguish between the effects of three possible sources of bias: omission of a balanced covariate, data censoring and unmeasured confounding. Asymptotic formulae for determining the bias are derived from the large sample properties of the maximum likelihood estimator. A simulation study is used to demonstrate the validity of the bias formulae and to characterize the influence of the different sources of bias. It is shown that the bias converges to fixed limits as the effect of the omitted covariate increases, irrespective of the degree of confounding. The bias formulae are used as the basis for developing a new method of sensitivity analysis to assess the impact of omitted covariates on estimates of treatment or exposure effects. In simulation studies, the proposed method gave unbiased treatment estimates and confidence intervals with good coverage when the true sensitivity parameters were known. We describe application of the method to a randomized controlled trial and a non-randomized study.
Institute of Health Research
Collections of Former Colleges
Item views 0
Full item downloads 0
Related items
Showing items related by title, author, creator and subject.
-
Diet analysis of two data deficient stingray species, the southern stingray (Hypanus americanus) and the Caribbean whiptail ray (Styracura schmardae), with methodological insights into the use of stomach content analysis and stable isotope analysis
Wrigglesworth, E (University of Exeter Biological Sciences, 18 March 2019)The study of animal diet has long been a fundamental area of biological sciences and has developed significantly over the centuries. An understanding of animal diet goes beyond species-specific biology providing insights ... -
A Comprehensive Analysis of Policy Diffusion: Regulatory Impact Analysis in EU and OECD Member States
De Francesco, Fabrizio (University of Exeter Politics, 23 July 2010)Among the tools available to enhance the rationality of policy formulation, Regulatory Impact Analysis (RIA) has captured the attention of many scholars for its potential to enhance the accountability and transparency of ... -
An International Relations Analysis of Citizenship and Intercultural Dialogue among Minority Youth in Berlin and London: A Levels-of-Analysis Approach
Difato, Christine Anne (University of Exeter Exeter Centre of Ethno-Political Studies, 30 September 2012)Corresponding to the rising threat of terrorism and heightened security concerns throughout Europe, potential parallel communities have come under increased scrutiny and pressure to engage and integrate in the politics and ...